Answer:
Carbonic acid
Step-by-step explanation:
Hello,
In this case, due to the increasing concentration of carbon dioxide in the atmosphere, when it rains, the following chemical reaction occurs between water and carbon dioxide:
![CO_2+H_2O\rightarrow H_2CO_3](https://img.qammunity.org/2020/formulas/chemistry/middle-school/texnrin5urrb99p097ssnjdjbyqa9nohv6.png)
Whose product is known as carbonic acid and it is the natural source of acidity in acid rain.
Regards.